The ojectives of this work are to provide a better understanding of the hydrodynamic behavior of circular and denatured DNA forms in aqueous electrolyte solution. Various forms of circular DNA's are being isolated from natural ssurces or produced artificially from naturally occurring DNA's. Viscosity and sedimentation measurements are being employed to study the hydrodynamic behavior as a function of such parameters as pH, number of superhelical turns per unit molecular weight, ionic strength, and concentraton of intercalating small molecules. Recent studies in the course of this work have shown that bacteriophage PM2 has a number of properties which should establish it as an excellent model system for comparison with the circular DNA-containing oncogenic viruses polyoma and SV40, and the papillloma viruses. These properties all of which have been seen in the oncogenic circular DNA-containing viruses, include superhelix density heterogeneity in the replicating DNA, catenated circular forms in the replicating DNA, and the presence under certain conditions of nucleoprotein particles from which part of the protein envelope has been removed. Hydrodynam c, electronmicroscopic, and sedimentation equilibrium techniques will be employed.